This invention relates to a process for the preparation of orthophenylphenol and its derivatives. More particularly, it relates to a process for the reaction of dibenzofuran and its derivatives with hydrogen, at elevated temperatures, in the presence of a catalyst comprised of one or more Group VIII elements.
Dibenzofuran may be represented by the following formula numbered according to Chemical Abstracts (1973) ##SPC1##
Under the influence of a catalyst a hydrogenolysis reaction takes place, whereby one of the two carbon-oxygen bonds of the furan structure in dibenzofuran may be cleaved with the subsequent addition of hydrogen to each of these sites, for example, the bond between the numbered members (5) and (5a) or (5) and (4a) may be cleaved with subsequent addition of hydrogen to form orthophenylphenol product.
It will, therefore, be understood that derivatives of dibenzofuran used in this process of the present invention for preparing derivatives of orthophenylphenol should include a heterocyclic ring of at least five members with oxygen being the hetero atom, and the ring thereof containing unsaturation at each of the carbon atoms attached to said hetero oxygen atom. It should also be understood that the carbocyclic rings in dibenzofuran and its derivatives may be partially saturated so long as the heterocyclic ring oxide contains unsaturation at each of the carbon atoms attached to said hetero oxygen atom.
The derivatives of dibenzofuran for the process of this invention may be represented by the formula ##SPC2##
Where n is an integer from 0 to 2, m is an integer from 1 to 2, and each R may be selected from cycloalkyl of 5 to 7 carbon atoms, alkylated cycloalkyl of 6 to 11 carbon atoms, phenyl, benzylphenyl, diphenylyl alkylated phenyl of 7 to 19 carbon atoms, naphthyl and alkylated naphthyl of 11 to 14 carbon atoms.
The following substituents are illustrative of those which may be represented by R; cyclopentyl, cyclohexyl, cycloheptyl, 2-ethylcyclohexyl, 2-ethylcyclopentyl, 3-propylcycloheptyl, 1-methyl-2-ethylcyclohexyl, phenyl, benzylphenyl, diphenylyl, tolyl, ethylphenyl, isopropylphenyl, n-hexylphenol, 3-methyl-hexylphenyl, cumyl, 2,6-diisopropylphenol, 1-naphthyl, 2-naphthyl, methylnaphthyl, ethylnaphthyl, t-butylnaphthyl, dimethylnaphthyl or the like.
It should be noted that, in addition to the R substituents, the carbocyclic rings may contain a lower alkyl substituent straight chain or branched such as methyl, ethyl, propyl, isopropyl, butyl or an oxygen containing substituent such as hydroxyl, carbanol, aldehyde, carboxylic acid and the like.
R may also represent the addition of a 4 carbon chain in such a manner as to effect the formation of a benzenoid type fused ring structure giving rise to such compounds as dinaphthofurans, benzonaphthofurans and substituted derivatives thereof.
It will also, therefore, be understood that Group VIII elements used in the process of the present invention for preparing orthophenylphenol and its derivatives shall include one or more of the following named elements: platinum, palladium. iridium, osmium, rhodium, ruthenium, nickel, iron, and cobalt.
Orthophenylphenol and its derivatives are useful for the preparation of dyestuffs, for example 2,2'-dihydroxydiphenyl which is described in U.S. Pat. No. 3,169,149. Orthophenylphenol is also useful as an antimicrobial agent, for example, as a fungicide for the postharvest treatment of citrus fruit [McCornack, Proc. Fla. State Hort. Soc., 83, 229- 32 (1970)], as a biocidal agent or preservative for wood chips (U.S. Pat. No. 3,481,686), or admixed with other phenolics for the preparation of synthetic detergent-disinfectant or germicidal agents (U.S. Pat. No. 3,824,190).
Addition of hydrogen to furan compounds may proceed by way of a hydrogenation reaction to produce partially saturated or saturated compounds and by way of a hydrogenolysis reaction which involves cleavage of the carbon-oxygen bond or bonds and cleavage of carbon-carbon bonds. The prior art is replete with examples of both types of reactions using both catalytic and noncatalytic systems. Consequently it is obvious from the prior art that the hydrogenolysis reaction may be carried out in a facile manner for many of the furans, however, the prior art does not teach the hydrogenolysis of dibenzofuran, in particular, especially for the preparation of orthophenylphenol.
For example, a method for the cleavage of the furans at the carbon-oxygen bond is described in work done by Smith and Fuzek [J. Amer. Chem. Soc., 71, 415 (1949)] using a platinum catalyst in acetic acid solution in the presence of hydrogen. The reaction is carried out in a constant temperature water bath at low pressure. All the furans studied in this work are successfully cleaved using this method with the exception of dibenzofuran. The product of the reaction when dibenzofuran is used as a substrate involves the hydrogenation of both phenyl nuclei to give dicyclohexylene oxide. This is the only furan studied which does not cleave to a major extent.
Another method known in the art is the hydrogenolysis of dibenzofuran to give orthophenylphenol by way of reacting lithium metal with dibenzofuran in refluxing dioxane to form the lithium derivative of orthophenylphenol. followed by water-dioxane hydrolysis to give orthophenylphenol and other side products. This work was carried out by Gilman and Esmay [J. Amer. Chem. Soc., 20, 2947 (1953)]. Since the reaction of this process requires stoichiometric amounts of the alkali metal, the process cannot compete economically with the process of this invention.
The prior art as taught by Landa and co-workers [Sb. Vysoke Skoly Chem.-Technol. Praze, Technol. Paliv, 16, 159-70 (1969)] discloses that MoS.sub.2 has been used as a catalyst for the hydrogenolysis of dibenzofuran to give orthophenylphenol. The reaction cited was carried out in a batch reactor charged with about 29 grams (0.17 moles) dibenzofuran and 4 grams MoS.sub.2 having a surface area of 31 m.sup.2 /gram. The reaction was allowed to continue for 30 minutes at 300.degree. C and at a pressure that would be consistent with charging the reactor with 100 atmospheres of hydrogen gas at 17.degree. C. The resulting product consisted of partially saturated and saturated derivatives of dibenzofuran as well as orthophenylphenol, the selectivity to orthophenylphenol product was only 33% at a conversion of 66%. A distinct advantage of the process of this invention over this prior art is the favorable selectivity of this invention to form orthophenylphenol.
The prior art according to Chandler and Sasse [Aust. J. Chem., 16, No. 1, 20 (1963)] teaches the use of Raney nickel for the hydrogenolysis of dibenzofuran by refluxing in methanol in the presence of hydrogen for about 16 hours. No orthophenylphenol is obtained. Instead, a partially saturated product is produced, namely phenylcyclohexanol. The disadvantage of this process, when compared to the process of this invention is the necessity of a dehydrogenation step in order to obtain the desired product of this invention. Thus Chandler and Sasse would require a two step process. The present invention teaches a viable one step process for the production of orthophenylphenol.
Likewise, Popa, Schwenk, and Ginsburg [J. Org. Chem., 16, 253 (1951)] carried out experimental work in which hydrogenolysis of the carbon-oxygen bond in furan compounds was brought about in the presence of nickel-aluminum alloy and aqueous alkali. These compounds yielded approximately equal amounts of two products, one resulting from the hydrogenation of the furan ring, the other a product of the hydrogenolysis of the furan ring. Of the furans tested, only dibenzofuran was substantially unreactive, i.e., only a small amount of phenolic material tentatively identified as orthophenylphenol was obtained. On the other hand, coumarilic acid, unlike dibenzofuran, gave good yields of its hydrogenolysis product .beta.-(orthohydroxyphenyl)-propionic acid. Here again, as described in the work by Chandler and Sasse as well as Smith and Fuzek, little if any of the desired product is being formed in a one step reaction of the type described for the process of this invention.
Other approaches involving classical organic syntheses are described in the prior art, however the methods employed may result in the formation of the mixed isomers, i.e., ortho, para, and metaphenylphenol. This would not be desirable from the standpoint that of the three isomers formed, orthophenylphenol is the most effective as a biocidal agent. The other isomers, i.e., para- and metaphenylphenol, have been demonstrated to be biocidal agents with lesser degrees of effectiveness and, therefore, would only serve as diluents for this application. In addition the para and meta isomers would represent a product loss for the utility of the present invention, since the primary product desired is orthophenylphenol.
Application of Group VIII elements in the form of supported catalysts for the hydrogenolysis of simple furan structures, e.g., 2-methylfuran or 2-vinylfuran, is described in the art by Shuikin, Bel'skii, and Minachev, [J. General Chem. USSR, 29, 2932 (1959)]. For example, the hydrogenolysis of 2-methylfuran is carried out in the vapor phase at 275.degree. C in the presence of a platinum on carbon catalyst and hydrogen to give a substantial amount of methylpropyl ketone product. Here again, however, only simple furan compounds were successfully cleaved at the carbon-oxygen bond.
It has now been found that control of conditions is important, i.e, rising temperature favors the hydrogenolysis reaction, while decreasing temperature favors the hydrogenation reaction. Likewise the pressure may serve an important function in the reaction. Most importantly, for the process of this invention, is the ability to select a combination of catalyst and conditions that will selectively cleave the furan ring in dibenzofuran and its derivatives at the carbon to oxygen linkage without substantially hydrogenating the unsaturated portion of the structure or without cleaving the phenyl to phenyl linkage previously designated as the bond between carbons 9 a and 9b.
It is, therefore, an object of the present invention to overcome the above disadvantages and thus provide an improved and more economical and commercially feasible hydrogenolysis process for the production of orthophenylphenol and its derivatives from dibenzofuran and its derivatives.
Another object of this invention is to provide a catalyst system for a viable one step hydrogenolysis process for the production of orthophenylphenol and its derivatives from dibenzofuran and its derivatives.
Another object of this invention is to provide a reactive, yet stable hydrogenolysis catalyst system that may be operated selectively to produce high yield of the preferred orthophenylphenol product.
These and other objects of the present invention will become apparent to those skilled in the art from the accompanying description and disclosure.